1. Field of the Invention
This invention relates to wired or wireless communication networks, such as, cellular mobile radio system networks and, more particularly, to locating mobile end users, or subscribers, and routing messages to such cellular subscribers as they roam between communication networks such that voice, data or mail messages follow them or locate them automatically within such networks without the originator having to know the address location of the target user, the type of device, or the network involved, or without the target user having to initiate the retrieval of the message.
2. Description of the Background Art
In order to present a complex example, a wireless network using cellular technology is described. The invention is not limited to wireless or cellular networks, but could be used in any network where the interconnecting, or intermediate, office can communicate with both an end user and the overlaying logical network. The logical network is the controlling entity that dictates message routing and form, and directs originating messages to their intended target based on end user inputs. The logical network is typically computer based and may be defined by a local or private company network which interfaces with a regional communication carrier, e.g. BellSouth.RTM., or by a private network service. Cellular communication is just one type of wireless network technology that utilizes and partitions available frequency bands into cells for transmitting messages, such as voice and data. Accordingly, other wireless communication networks are available that utilize available frequency bands in schemes other than cellular for the wireless transmission of messages.
Radio telecommunication, such as cellular, is a portable or mobile communication system employed by telephones, computers and facsimiles for interacting with existing telephone systems so that mobile users may communicate with other radio devices and with standard wireline telephones, facsimiles and computers. A networking technique is employed in cellular communication which includes covering entire countries or large regions with a system of radio telephones that broadcast over available frequencies on a frequency band around 900 MHz. These cellular radio networks are a mixed system wherein they simultaneously broadcast analog voice and data signals, and digital control signals to use available frequencies more efficiently. With reference to FIG. 1, in individual cellular radio networks a country or region is divided into a collection of cells 4 for frequency management, wherein each cell is approximately three miles thick and has its own radio transmitter or transceiver 3. Each radio transmitter is controlled by a mobile telephone serving office (MTSO) 1 including a central mobile switching computer which directs calls to the intended target device. With reference to FIG. 2, as a cellular communication device, or remote subscriber unit (RSU) 5, travels between cells a "handoff" of broadcast operating frequencies is performed by the MTSO 1 central computer so that the MTSO 1 can maintain a communication link with the RSU without jamming the frequencies or causing channel chatter. Each cell in a cellular network exchange is illuminated by radio transmissions from a particular MTSO base station covering that cell for communicating with RSUs in that cell. An MTSO is defined by a mobile switching center for accessing subscriber unit data information. The MTSO thereby controls the radio linkages between different MTSO base stations and their associated cells 4 covering a given geographic area. Thus, each cellular exchange or system 2 is comprised of one or more MTSO base stations and their MSCs which serve the RSUs within a particular geographic area.
Referring to FIG. 2, in a conventional cellular communication network when the RSU is the originating cellular device, or RSUO 5, the cellular message is transmitted from the RSUO 5 as an analog signal to the cell transmitter 3 in the originating cell. The message is transmitted to a target transceiver 3 and eventually sent along conventional telephone lines to the target exchange, or MTSO. The MTSO typically converts the message to digital for switching and sending the message to the correct target destination. After switching, the signal may be reconverted to analog for airlink transmission or remain digital and sent along telephone lines. It should be noted that a similar, but reversed, path is followed when the originator is a wireline device calling a cellular target, or RSUT 6, whereby the signal is first sent through the direct lines and then transmitted from a transceiver to the target RSUT 6. If the target device is a conventional wireline phone or computer 6a, then the message continues along the carrier telephone lines, such as a regional bell operating carrier or private data service 8, to the wireline target. On the other hand, if the target device is also a cellular RSU, RSUT 6, then the message is sent to the MTSO radio transmitter for transmitting to the target cell transmitter 3 and target RSUT 6.
When the cellular RSU leaves its registered calling area or MTSO exchange, the device is said to be roaming. When roaming, it is desirable to provide telephone or communication service to the RSU to allow the RSU to originate calls to other RSUs or wireline subscribers, or to receive communications from other subscribers. Roaming is a conventional technique in which an RSU may be tracked to any MTSO exchange or geographic communication area outside its home MTSO. Exchanges outside the home exchange are known as visited exchanges. Roaming allows any cellular user to access the cellular radio system from any visited exchange in the country via different networks. However, when roaming a RSU must register with the visited exchange for tracking and identification purposes. An RSU may pre-register with a predetermined visited exchange before entering that exchange or may be configured for automatic registration whereby RSU identification codes are automatically transmitted and recognized by the visited MTSO. Additional fees are often incurred by an RSU end user when roaming because MTSO exchanges often charge a visitor for registration, for tracking and the number of communication links that must be made.
Based on the above-noted, current cellular communication systems may be described as comprising physical cellular networks and logical networks. Although cellular networks may be broken down into the physical and logical world, both the physical cellular network and logical networks overlap and work hand in hand, as noted above. For example, the MTSO exchange maintains a home location register (HLR) typically defined by a computer for mapping phone numbers with device serial numbers. Therefore it may be categorized into both the physical and logical world. At the same time, however, both the physical cellular network and logical networks perform distinct functions in today's technology. The physical network comprises conventional wireline and cellular radio telecommunication connection systems, such as those operated by large phone carrier service corporations, to transmit either voice or data-type messages between end users over communication cables, fiber optics or air-link channels. The physical cellular network may route voice or data message between an originating fixed or wireline connected communication device, such as a telephone, a computer having a modem, or a facsimile, and an RSU, such as a cellular phone, portable computer with cellular communication capabilities or portable facsimile, or between two mobile devices, such as those noted above. The physical cellular network establishes communication links between end user devices through direct physical links, such as PSTN, and air links, such as CDPD, based on a specific device address and current location that appears to be "fixed" (immobile) to the physical network on each end at any given instant. Regarding air links, the cellular RSUs in the mobile subscriber networks maintain communication with one another and with direct line devices connected to the PSTN or CDPD by virtue of radio links. In the past, the PSTN networks were merely used by telephone companies to establish direct telephone connections over wireline systems. More recently, CDPD networks have been employed, especially in computer to computer communications for sending voice and data messages in digitized data packets over airway transmissions accessed through a wireline gateway computer.
The logical networks comprise public and private logical control systems which are manipulated by end users to select a desired operating function and target address for transmitting or receiving desired messages or for temporarily registering with new networks when roaming. The logical networks typically in place cooperate with the physical networks to direct calls or messages and to establish telecommunication links between subscriber end-users whether RSUs or fixed line devices. Conventional logical networks include home location registers (HLR's) and visitor location registers (VLR's), i.e. the MTSO, which store or maintain a register of electronic serial numbers (ESN's) of mobile devices (RSUs) registered in the corresponding network and of those mobiles roaming the network exchange that automatically register or pre-register. The ESN is the identification number of the device only and it is transmitted over a control channel. The HLR and VLR is nothing more than a computer database. Essentially, when an originator dials a target's phone number the originating ELR correlates the phone number with the ESN based on a logic map and then locates that ESN through the physical network. If the ESN is not located in the boundaries of the current cellular network then the originating HLR must ask other VLR's of other networks if they have the target ESN. If a target VLR has the target device then it either authorizes or does not authorize the call depending on factors such as payment history or current registration status. Therefore, with present technology, cellular communications between different carriers or network must pass through an originating device's own operating logical networks as well as the cellular target's operating logical network before reaching the target RSU. This is because under current telecommunications technology, a "phone number" specifies a "route" to a device. As a user "roams," the "route" must be flexible. The ESN and HLR/VLR databases are used to give flexibility to the route. Each time an HLR responds to a request it charges the requesting VLR which, in turn, passes the cost down to the users regardless of whether an authorization is made. In addition, the originating user is limited to finding the target device rather than the actual user.
Each mobile subscriber, or RSU, is associated with a particular home MTSO and an HLR. The home network has registers which maintain records of all relevant information associated with the mobiles, including the type of telephone service and options they have been programmed to receive. For example, a home network stores a mobile subscriber's mobile identification number ("MIN") along with its electronic serial number ("ESN") identifying the particular mobile instrument for determining the categories of service which it is contracted, e.g., call forwarding, call waiting, long distance calling in areas, originating features to selected exchanges, and other subscriber specific information. When the RSU is operating within its own network, i.e., geographic area, and calls are being handled through its home MTSO, all of this information is available in the HLR and is used by the MTSO in handling telephone traffic between base stations and with the target mobile. The MIN and ESN's are transmitted over a control channel for identifying the device and is subsequently used for handling billing. These identification numbers, however, do not identify the actual user. Therefore, the devices may be fraudently used. In addition, originators can only locate and route messages to the target device and not necessarily their intended target user. There is essentially a gamble that a transmitted message from the originating device will ever reach the user. In addition, if a target device is not enabled then the message has no way of automatically reaching either the target user or device. Although the home HLR records the last known geographic exchange location of the mobile, the last known location of the RSU is useless when power is off since location changes and a directed call going through the physical cellular network and logical networks of both the originator and target devices (i.e. RSU) may have changes imposed. In addition, storing the last known location of the RSU does not enable the routing of messages to the RSU target user once the user is activated.
The location registers of each cellular network, as defined by the MTSO 1 of FIGS. 1 and 2, communicate and request user specific information from other HLR's and a visiting device seeks temporary registration in the network. The home HLR 4 device stores the devices MIN and ESN numbers and cell location information of RSUs, while the peer VLR's store temporary device and location information of RSUs currently visiting the exchange. The information requests from or between location registers includes the user ID, MIN and ESN codes, and whether that device is currently registered with its home HLR or the contacted HLR and if it is authorized to make calls or is temporarily registered and located in that network. Each time a home or peer HLR of a network responds to information requests the responding network charges the requester. The same problems exist when calling from an RSU to an RSU number outside the home network because the home carrier network, typically a regional bell operating carrier (RBOC) has to go through a long distance carrier service, as seen in FIGS. 3 and 4, to make a communication link. And, before that link is established the HLR's must compare the phone number dialed to the target device MIN and ESN numbers to find the device. Once again, it is more expensive than conventional direct line calls and requires time and requests response sequences to find the target device; not necessarily the user. RBOC's cannot carry long distance traffic. Therefore, they must use long distance carriers which eventually link to the corresponding or responding networks for user traffic, and a separate network for signaling (HLR/VLR) traffic. The present invention, therefore, provides "middle man" devices which temporarily store device and device location information, user identification information, and user traffic transport and data information. This information is made available to any requesting control office or port when the originator originates a call through an initiating service office.
Polling describes tracking schemes used for maintaining communication between roaming RSUs and cellular communication system networks, or MTSO's. In polling schemes, each RSU periodically receives a signal referred to as a system identification number (SID) in North American cellular systems, from a MTSO base station which includes data information that identifies the particular polling scheme and base station with which the RSU is in current radio contact. The RSU in turn responds to the periodic signals transmitted from the base stations by transmitting its MIN and ESN back to the base station for temporary registration with it as a user. The receiving MTSO records an indication of the presence of the RSU in the visited exchange area inside a memory location. This informs MSC base stations in the geographic exchange area of the presence of the RSU within its coverage area at that particular moment. Cellular systems can only trace an enabled device, not the user, and the device must be in some way registered each time to be recognized. There are basically three ways in which an RSU may register with a base station. The first is an autonomous registration which is used in response to the RSU entering a new exchange area. The second way a RSU registers is by a periodic registration which is typically in response to the passage of time elapsing since the last or previous registration. And, the third registration scheme occurs while originating a call or message transfer from the RSU in response to an unregistered RSU seeking to originate a call, or establish a communication connection. In either event, any calls or messages looking for the device must be verified by the visited HLR and authorized by the home HLR. An authorization is not guaranteed, takes time and is costly. Some solutions suggest registering with a number of MTSO's. This, however, does not eliminate the problem of tracking users, finding disabled devices when a message is originated and alleviating the high cost associated with responding HLRs.
Thus, as a cellular user travels with their cellular phone on, the phone reports itself to every cell it passes and to MTSO base stations as it changes networks. So at a physical level the network knows the phone's cell location. However, at the logical and physical level the cellular network system, does not necessarily know the location or identity of the target user and if the target device is off at the time a message is originated, the message may never be received. So messages may or may not reach the user. Moreover, current environment logical networks require active users to directly interface with the logical network via the communication devices, i.e. phone or modem interface, to retrieve or forward messages. For example, in cellular communication devices having auxiliary features such as call forwarding, electronic mail, facsimiles or other data retrieval features, the target end user has to pre-program their phone or modem based communication device to direct calls to a desired target address, keep their communication device powered, and remain within the required calling area of the cellular target device. In phones having call forwarding features the user must reprogram the phone to forward calls to a preestablished phone address. Although a caller may establish a connection with a cellular phone user with call forwarding, they cannot necessarily transmit messages, and once the cellular phone is powered down, then the originating end user has no way of determining the cellular user's location. In other words, the present cellular telecommunication systems do not have the ability to locate or monitor the location of remote cellular users for routing or transmitting messages, or for automatically transmitting messages once a location is known.
Accordingly, there remains a need for a cellular mobile radio system or network that locates cellular subscribers, and which can automatically route messages to remote subscriber users without the originator having to know the address location of the user or the type of target device being used, or the target user having to initiate the retrieval of the messages. Although there exists systems in the background art which maintain or store the location of cellular devices, those systems known in the background art do not address these problems noted by the present invention. For instance, Hayes et. al., U.S. Pat. No. 5,210,787, discloses a subscriber interrogation point system for use in cellular networks that maintains a database of home exchange locations for mobile subscribers and that communicates this information to mobile switching center exchanges visited by the mobile subscribers to simplify database maintenance. The subscriber interrogation points store in memory information associated with each mobile subscriber identifying either the home exchange of that particular subscriber or other subscriber interrogation points able to identify such home exchanges. Thus, Hayes, et al provides an address resolution scheme for managing database information relevant to mobile subscribers thereby keeping a map of devices in its area. Unlike the instant invention, Hayes et. al. updates geographic locations of mobile devices and visited exchanges, updates the mobile device's home exchange, authenticates the mobile device as being capable of receiving service from the visited exchange and obtains information as to the detail service specifications which the visiting mobile subscriber is to receive. Thus, Hayes et. al. maintains a database of device specific information. Hayes et. al. does not provide a "find me" technique applied at the logical level for automatically locating users and routing messages, whether voice or data, to the users of remote subscriber units as they roam between networks. By contrast, the instant invention incorporates regional and local offices in a fully meshed communicating network which locates end users and routes messages to the user of a device independent of the actual device being used without the actual target user and originating user having device specific information related to each other.
Other devices and systems noted in the background art include U.S. Pat. No. 5,153,902 issued to Buhl et. al., U.S. Pat. No. 5,255,307 issued to Mizikovsky, U.S. Pat. No. 5,150,362 issued to Akerberg, U.S. Pat. No. 5,307,400 issued to Sawyer et. al., U.S. Pat. No. 5,212,822 issued to Fukumine et. al. and U.S. Pat. No. 5,222,249 issued to Carney. Buhl et. al., in U.S. Pat. No. 5,153,902, discloses a multi-exchange paging system for locating a mobile telephone in a wide area telephone network. The disclosure of Buhl et. al. describes a method of optimizing a sequence of areas a poll is sent to find the physical communication device. Unlike the present invention, Buhl et. al. assumes a predetermined list of areas. By contrast, the instant invention addresses the way a logical network is traced to find a logical subscriber and provides a system that searches a network in a novel, optimal way using pre-existing physical network polling techniques at the physical level. Mizikovsky, U.S. Pat. No. 5,255,307, discloses a status indicator control for cellular mobile telephone systems which provides a HOME indication when the mobile is in its home system and a ROAM indication when the mobile station communicates with a base station in a visited system whereby the particular indication is dependent upon the system identification data received from the base station. Thus, Mizikovsky teaches a method to allow the HOME/ROAM indicator to be controlled programmatically and it allows for the indicator to be changed when the phone is in an active mode and when the protocols are changed between home and roam. Akerberg, U.S. Pat. No. 5,150,362, discloses a beacon carrier which assigns time slots or channels to a mobile unit after the mobile unit and relevant base station have established communication, that is, have found each other. Sawyer et. al., U.S. Pat. No. 5,307,400, teaches call routing in mobile telephone systems whereby a mobile unit initiates a communication contact and registration process. In Sawyer et. al., a visiting mobile subscriber sends a registration access, the visited system acknowledges the registration, records the mobile subscriber's presence and signals the mobile subscriber's home system of the mobile's presence. Thus, Sawyer et. al. initiates the communication link with the visited exchange and the registration process. By contrast, the instant invention provides a logical network system and method that communicates with regional and local offices or nodes that are able to find mobile cellular users and automatically transmits messages to the users through the logical network. Fukumine et. al., U.S. Pat. No. 5,212,822 discloses a method for registering mobile stations in mobile communication systems by pointing a mobile unit to a preferred base station when an overlap exists between stations within the same communication network. Carney, U.S. Pat. No. 5,222,249, discloses a method and system for providing dynamic RF communication resources to a mobile unit as that mobile unit changes geographic areas such that RF communication resources used by that mobile unit are not forcibly terminated as that mobile unit roams. Carney, therefore, teaches a method for channel reassignment during handoff that attempts to insure channel resources will be available at the target cell by tracking the mobile unit and anticipating cell boundary crossings. Although today's cellular telecommunication systems can locate a cellular device and establish a physical cellular network link, the logical networks and their interaction with the physical networks is very limited. More specifically, conventional cellular communication systems can only locate the cellular device and not the actual user, they cannot forward messages to cellular target devices without inputs from the target end users, messages cannot be automatically forwarded to a cellular target device without the target user calling into their home location to initiate the process, direct connections cannot be directly established between cellular users of different carriers, and a cellular target user is not able to authorize, or filter, messages that are allowed to find the target device. Moreover, the carriers do not know the location of their remote cellular end users until the actual user turns on their power, after which the carrier must search for the user in a hierarchy priority search. The present invention represents a novel logical network system for use with existing physical cellular networks and a method which automatically interfaces the new and existing logical networks, such as International Business Machine's (IBM.RTM.) Intelligent Communications Systems (ICS) (trademark of IBM.RTM.), with remote subscriber units, or targets, through the physical network and routes messages to the actual user of the target RSU instead of just the device and which may store messages for target users whose location may be unknown when messages are originated and automatically transfer the message to the target user when they are relocated and activated.